Digital Video Broadcasting (DVB) systems distribute data using a variety of approaches, including by satellite (DVB-S, DVB-S2 and DVB-SH), DVB-SMATV for distribution via SMATV), cable (DVB-C), terrestrial television (DVB-T, DVB-T2), and digital terrestrial television for handhelds (DVB-H, DVB-SH). The associated standards define the physical layer and data link layer of the distribution system. Devices interact typically with the physical layer through a synchronous parallel interface (SPI), synchronous serial interface (SSI), or asynchronous serial interface (ASI). Data is typically transmitted in MPEG-2 transport streams with some additional constraints (DVB-MPEG).
The distribution systems for the different DVB standards differ mainly in the modulation schemes used and error correcting codes used, due to the different technical constraints. For example, DVB-S (SHF) uses QPSK, 8PSK or 16-QAM. DVB-S2 uses QPSK, 8PSK, 16APSK or 32APSK, based as a broadcaster's option. QPSK and 8PSK are the only versions regularly used. DVB-C (VHF/UHF) uses QAM: 16-QAM, 32-QAM, 64-QAM, 128-QAM or 256-QAM. DVB-T (VHF/UHF) uses 16-QAM or 64-QAM (or QPSK) in combination with COFDM and can support hierarchical modulation.
The DVB-T2 standard (e.g., “Frame structure channel coding and modulation for a second generation digital terrestrial television broadcasting system (DVB-T2),” DVB Document A122, June 2008) is an update for DVB-T to provide enhanced quality and capacity. It is expected that the DVB-T2 standard will provide more-robust TV reception and increase the possible bit-rate by over 30% for single transmitters (as in the UK) and is expected to increase the maximum bit rate by over 50% in large single-frequency networks (as in Germany, Sweden).
However, mobile services typically need lower bit rates with a greater number of physical level channels (e.g., physical level pipes) than services that may be currently supported by the DVB-T2 standard. Thus, there is a real market need to further enhance signaling capacity in order to support services for mobile devices with the available broadcast spectrum.